The study found that levels of radioactivity in the ash in the Illinois, Appalachian and Powder River basins were up to five times higher than in normal soil, and up to 10 times higher than in the parent coal itself because of the way combustion concentrates radioactivity.
The finding raises concerns about the environmental and human health risks posed by coal ash, which is currently unregulated and is stored in coal-fired power plants’ holding ponds and landfills nationwide.
Radium isotopes and lead-210 occur naturally in coal as chemical byproducts of its uranium and thorium content. The research team found that when the coal is burned, the radium isotopes become concentrated in the coal ash residues, and the lead-210 becomes chemically volatile and reattaches itself to tiny particles of fly ash. This causes additional enrichment of radioactivity in the fly ash.
Smokestack scrubbers installed at US power plants keep these contaminants from escaping into the air when the coal is burned, researchers say. But if the contaminated coal ash is spilled, or if effluents leak from ponds or landfills, it may pose a hazard.
The study comes as the EPA’s first-ever regulations on coal ash disposal are set to go into effect in October.
The peer-reviewed paper was published Sept. 2 in the journal Environmental Science & Technology.
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